French project completes first subhorizontal geothermal well near Paris

Drilling rig on site in Cachan, Paris/ France (source: Dalkia)
Alexander Richter 4 Jan 2018

French engineering firm GPC IP successfully designed and supervised the first subhorizontal geothermal well successfully drilled for Dalkia in the Paris Basin, France.

A release reported today that the first subhorizontal geothermal well was successfully completed at Cachan in the Paris Basin in France.

Drilling for the well started on 13 December 2017 with the design and under the supervision of GPC IP, a Paris/ France-based engineering consulting firm founded in 1998. The customer is Dalkia, a company under the EDF Group.

The design of the well is a first for geothermal engineering, as it achieves a 1,001 m long, 87° slanted, 8″1/2 openhole drain in the Dogger/Bathonian, Mid Jurassic, oolithic limestone, target reservoir, at a 1,550 m true vertical depth.

The new geothermal doublet (two wells) for the DALKIA/City of Cachan JV (DALKIA operator) in Cachan, is expected to replace existing ageing equipment. “This is a world first,” said Jean-Philippe Buisson, regional director of Dalkia, a subsidiary of EDF, co-delegated with Socachal, for the heating network. We have just completed a phase of horizontal drilling over 1,000 m in the groundwater of the Dogger ( NDLR aquifer below the Paris Basin) at 1,600 m depth. This is the first time that this technique has been used until now reserved for oil drilling. Usually, the angle is 40 degrees during traditional drilling.

The concept, first published in February 2011 (*) at the Stanford Geothermal Engineering Workshop, proved rewarding, further to well tests, evidencing a 450 m3/hr nominal discharge and a 16 MWth rated capacity.

The advantage is to drain more hot water over a long length. Thanks to these techniques, the flow will be doubled and the production of heat increased. A single doublet (two wells) will replace the two existing doublets (four wells) drilled 34 years ago. At least 400 m 3 / h of hot water will be expected with the two new wells, against 300 m 3/ h with the four old wells. Sub-horizontal drilling also significantly reduces the duration of the work: four months against eight to drill two doublets. The goal is to increase the number of subscribers by 15% over the coming years.

This well will be further replicated by an injection well of similar architecture.

The works began at the end of September 2017 and will end in February 2018. The investment volume for the new drilling campaign for Dalkia is around EUR 19 million ($22.4 million), of which 30% is covered by the heat fund set up by the ADEME and the Region.

The wells drilled and the plant will cover the heating and hot water needs of more than 7,000 housing equivalents (public facilities, apartment buildings and businesses) with expected start of operation in October 2018.

* Geomodelling and Well Architecture, Key Issues to Sustainable Reservoir Development. P.Ungemach, M.Antics et al. (2011)

We congratulate Pierre Ungemach and Miklos Antics of GPC IP on this achievement.

Source: release sent by email, Le Parisien